High power piezoelectric axial shockwave generation

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Stand 3.3 Single der Technik end piezo-shock-generatorThe above mentioned symmetrical generator setupcan be modified towards a single ram element witha nearly doubled energy and impulse output. This isdone by applying a bigger mass for supporting thePZT-stack at one side (seismic mass). The impulsewill be reflected there and directed towards theother output. A double pulse is created bycontaining nearly double the pulse energy (byelongating the total pulse output duration). Thecompensating impulse is transferred to the seismicmass as recoil (similar to a rifle).Design of a single end piezo-shock-generatorSeismic bodyHigh powerPZT-stackInternalprestressRam Steeltitanium brassPZT-stackCasingElectricalwiringImpuls reflectionLDA-spotSteel rodFigure 6a: Schematic of a single output piezo-shockgenerator.Seismic mass SMElectricpower switchHVcurrentpulsStraingaugeHVPTriggersignalFigure 5: Schematic of a single end piezo-shock-generatedsystem by application of a seismic mass. The interactionof the travelling pulses results in an elongated double pulseoutput.Figure 6b: Single ouput piezo-shock-generator: brass part:seismic countermass.8
Characterizing piezostackbasedshockwave generators4The piezo-mechanical performance parameters of apiezo-shock-generator can be derived straightforward from the characterization of piezo-stackactuators.●●Free ram stroke:Depends on PZT-stacks length, the applied electricalfield strength and type of the used PZTceramics. Strokes are ranging from µm to hundredsof µm.An efficient energy transfer must be completedwithin this stroke range limit.Piezo-shock-generators need therefore hard collisionpartners.Internal starting force:Generated force level within the PZT-bar uponcomplete electrical charge transfer.When the electrical rise-time is significantly shorterthan the shock generator's mechanical risetime,the initial force corresponds to an actuator'sblocking force. It depends mainly on stack'scross section, applied electrical field strength andtype of used PZT material.This starting force accelerates then the massesof the active PZT rod.●●●●●Pulse-width:= shock propagation time through the active PZTrod.It depends therefore on speed of sound in thePZT stack and stack's length.By pulse reflection at a seismic base, the resultingpulse length is doubled.Particle velocity:It corresponds to the maximum achievable shiftspeed of a piezo-actuator.Order of magnitude: several m/s.Mechanical energy content:It depends on volume or mass of the PZT-stack,the applied electrical field strength and the propertiesof the PZT ceramics.Impulse content P of the mechanical shock:P = moved mass within the shock front multipliedby the related particle velocity.Order of magnitude: kgm/s.Piezo-ceramics:High dielectric, high strain PZT materials providea much higher shock energy density than "lowcapacitance" actuator PZT materials (up to afactor 2).9
Page 1 and 2: High power piezoelectric axialshock
Page 3 and 4: Stand der01Piezo-Multilayer-Technik
Page 5 and 6: 2.2 Collision mechanicsIn practice,
Page 7: 1.1 3.2 Piezostapel Symmetrical mit
Page 11 and 12: 5. Electrical pulse excitationSchem
Page 13 and 14: 056.1 Experimental set upHigh volta
Page 15 and 16: 6.3 Single output shock generationT
Page 17 and 18: Stand der08Piezo-Multilayer-Technik
Page 19 and 20: 9.1 Impact propagation in the ideal
Page 21 and 22: 9.2 Stress impulse generation by a

High power piezoelectric axial shockwave generation

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